Restoration of 1952 MG TD 2

ETRIC threads Well as everyone except me already knew, it turns out that all the threads used on the engine are metric threads - mostly 8 x 1 metric fine, but also some 10 x 1·5 - but you use Whitworth or BSF spanners, as befits a classic English sports car. It took me a disappointingly long time to realise this, and probably quite a few stripped threads as I tried to match BSF and metric threads.

I wanted to write a clever pun about threads - it would have involved the interweaving threads, the warp and the woof that make up the rich tapestry of life to make this sad story of non-standardisation - but I wasn't clever enough ....

Anyway, this story begins in Connecticut in 1826 with the birth of Benjamin Hotchkiss. Like many Americans, even to this day, Hotchkiss was obsessed with weapons and armaments. Failing to interest the US government, he moved to France and established the Hotchkiss company there in 1867. After his death in 1885, his company continued to develop armaments, especially machine guns. The first model, displayed in 1892, was adopted by the French army in 1897, and was subsequently developed into the definitive Hotchkiss gun, a truly automatic, gas-operated heavy machine gun. By 1914, it had been adopted as the standard machine gun by British, French and Japanese armies. Whether they anticipated the hostilities which were to come, or whether it was a condition of sale to the British army, Hotchkiss established its armaments division in Coventry, naturally using the same machine tools as its parent, and replicating the metric threads. After the armistice, there turned out to be little demand for heavy gas-operated machine guns (could there be an opportunity here for an MBA thesis about losing your market by being too successful?), and Hotchkiss turned its knowledge and equipment to manufacture of engines.

At much the same time, in 1892 young William Richard Morris, then aged 15, began a bicycle repair business from his father's back shed, and later expanded it to include motorcycles. By 1910 he had expanded again to include motor car hire and repair under the name of WRM Motors Ltd, and soon began selling new cars as well. In 1912 he designed his first car, the two-seater Bullnose Morris, which used a 1018cc engine from White and Poppe. By 1914, however, a coupe and van needed bigger engines, and a 1548 engine was sourced from Continental Motor Manufacturing in Detroit. The same engine was used in the 4seat Morris Cowley and later Morris Oxford. Demand continued to grow throughout the war years, but after the war, possibly due to prohibitive import tariffs, Continental stopped supplying their motors. Morris bought the design rights, and persuaded Hotchkiss to build it in their Coventry works. At about the same time, he closed WRM Motors and allowed it to be absorbed into a new company, Morris Motors Ltd, and in 1923, pursuant to his policy of vertical integration, he bought the Hotchkiss works and incorporated it into Morris Motors as Morris Engines. (While there appears to be pretty broad agreement about these general facts, not all accounts agree with the chronology.) Hotchkiss continued to use their metric threads; but because only BSF/Whitworth hexagonal bar stock was readily available, they cut their threads into Whitworth stock, so that the metric nuts and bolts fit imperial Whitworth and BSF spanners. And a bit more than eighty years later, it's still giving me grief.